JP2017199728A - Separator for solid electrolytic capacitor - Google Patents

Abstract

An object of the present invention is to provide a separator for a solid electrolytic capacitor having a low short-circuit defect rate and high heat resistance.
A nonwoven fabric base material containing fibrillated heat-resistant fibers and synthetic short fibers as essential components, and a coating layer containing an inorganic filler provided on at least one surface of the nonwoven fabric base material. The solid electrolytic capacitor separator is more preferably a solid electrolytic capacitor separator in which the fibrillated heat-resistant fiber is a fibrillated wholly aromatic polyamide fiber.
[Selection figure] None

Description

  The present invention relates to a separator for a solid electrolytic capacitor.

  In a solid electrolytic capacitor using a conductive polymer such as polypyrrole or polythiophene as a solid electrolyte, a foil-like anode electrode and a cathode electrode are wound through a separator to form a winding element. By conducting the polymerization by impregnating the separator with a polymer solution of a conductive polymer, or impregnating the separator with a conductive polymer dispersion, a conductive polymer film that covers the separator is formed. Conventionally, as a separator of a solid electrolytic capacitor, a paper separator mainly composed of a beaten product of cellulose fibers such as natural cellulose fibers such as esparto and hemp pulp, solvent-spun cellulose fibers, and regenerated cellulose fibers has been used (for example, Patent Document 1). The cellulose fibers in these paper separators react with an oxidant used when polymerizing the conductive polymer to inhibit the polymerization of the conductive polymer, so that carbonization is performed in advance so as not to inhibit the polymerization. The For this reason, the carbon separator may be thermally shrunk or become brittle, so that burrs of the electrode may easily penetrate the separator, resulting in a high short-circuit defect rate.

  Therefore, as a solid electrolytic capacitor separator, a separator using a nonwoven fabric mainly composed of synthetic fibers has been studied (for example, see Patent Document 2). In recent years, in a solid electrolytic capacitor, the required temperature for reflow heat resistance has increased, but the separator of Patent Document 2 has a problem that heat shrinkage is large in a 260 ° C. atmosphere and heat resistance is low.

JP-A-5-267103 JP 2001-332451 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a solid electrolytic capacitor separator having a low short-circuit defect rate and high heat resistance.

  The present inventors have found the following invention as means for solving the above problems.

(1) It has a nonwoven fabric base material containing fibrillated heat-resistant fibers and synthetic short fibers as essential components, and a coating layer containing an inorganic filler provided on at least one surface of the nonwoven fabric base material. A separator for a solid electrolytic capacitor.

(2) The separator for a solid electrolytic capacitor as described in (1), wherein the fibrillated heat-resistant fiber is a fibrillated wholly aromatic polyamide fiber.

  According to the present invention, by using a nonwoven fabric base material containing fibrillated heat-resistant fibers and synthetic short fibers as essential components, the pores of the nonwoven fabric base material are reduced and formed relatively uniformly. The Therefore, the coating layer containing the inorganic filler provided on at least one surface of the nonwoven fabric substrate is uniformly formed on the nonwoven fabric substrate surface. The coating layer containing this inorganic filler can reduce the short-circuit defect rate of the solid electrolytic capacitor. Further, by including the fibrillated heat-resistant fiber and having a coating layer containing an inorganic filler, the thermal shrinkage of the separator can be reduced, and a separator having high heat resistance can be obtained.

  In the present invention, the expression “separator” means “a separator for a solid electrolytic capacitor”.

<Solid electrolytic capacitor>
In the present invention, the solid electrolytic capacitor refers to a solid electrolytic capacitor that uses a functional polymer having conductivity (conductive polymer) as an electrolyte. Examples of the functional polymer having conductivity include polypyrrole, polythiophene, polyaniline, polyacetylene, polyacene, and derivatives thereof. In the present invention, the solid electrolytic capacitor may be a combination of these functional polymers and an electrolytic solution. As the electrolytic solution, an aqueous solution in which an ion dissociable salt is dissolved, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), acetonitrile (AN), γ-butyrolactone (BL ), Dimethylformamide (DMF), tetrahydrofuran (THF), dimethoxyethane (DME), dimethoxymethane (DMM), sulfolane (SL), dimethyl sulfoxide (DMSO), ethylene glycol, propylene glycol, etc. Although what melt | dissolved salt, an ionic liquid (solid molten salt), etc. are mentioned, It is not limited to these.

<Separator for solid electrolytic capacitor>
In the present invention, the fibrillated heat-resistant fiber, which is an essential component constituting the nonwoven fabric substrate, is a wholly aromatic polyamide, wholly aromatic polyester, polyimide, polyamideimide, polyetheretherketone, polyphenylene sulfide, polybenzimidazole, poly A fibrillated heat-resistant fiber made of -p-phenylenebenzobisthiazole, poly-p-phenylenebenzobisoxazole, polytetrafluoroethylene, or the like is used. Among these, wholly aromatic polyamides are preferable because of their excellent affinity with the electrolytic solution. The degree of fibrillation is preferably a Canadian standard freeness of 0 to 400 ml as defined in JIS P8121. When the amount exceeds 400 ml, the fiber diameter distribution becomes wide, and there may be cases where the surface becomes uneven or thick, or the coating liquid used to provide the coating layer may be seen through. The length weighted average fiber length of the fibrillated heat resistant fiber is preferably 0.2 to 2.0 mm. If it is less than 0.2 mm, the nonwoven fabric substrate may fall off or the nonwoven fabric substrate may become fluffy, and if it is longer than 2.0 mm, it may become lumpy.

  Fibrilized heat-resistant fibers consist of refiners, beaters, mills, grinding devices, rotary homogenizers that apply shear force to high-speed rotary blades, cylindrical inner blades that rotate at high speed, and fixed outer blades. High-speed homogenizer that produces a shearing force between them, an ultrasonic crusher that is refined by impact by ultrasonic waves, a pressure difference of at least 3000 psi to the fiber suspension and a small-diameter orifice And by using a high-pressure homogenizer or the like that applies a shearing force or a cutting force to the fiber by causing it to collide and rapidly decelerate.

  In the present invention, the synthetic short fiber that is an essential component constituting the nonwoven fabric substrate is polyolefin, polyester, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyamide, acrylic, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, Examples thereof include short fibers made of resins such as polyvinyl ketone, polyether, polyvinyl alcohol, diene, polyurethane, phenol, melamine, furan, urea, aniline, unsaturated polyester, fluorine, silicone, and derivatives thereof, and the heat-resistant fibers described above. . Synthetic short fibers increase the tensile strength and puncture strength of the nonwoven fabric substrate.

  The synthetic short fiber is a non-fibrillated fiber, and may be a fiber (single fiber) made of a single resin or a composite fiber made of two or more kinds of resins. Moreover, the synthetic | combination short fiber contained in the nonwoven fabric base material of this invention may be 1 type, and may be used in combination of 2 or more type. Examples of the composite fiber include a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, and a multiple bimetal type.

  The fineness of the synthetic short fiber is preferably 0.007 to 1.1 dtex, and more preferably 0.02 to 0.6 dtex. When the fineness of the synthetic short fiber exceeds 1.1 dtex, the number of fibers in the thickness direction is reduced, so that it is difficult to reduce the thickness. When the fineness of the synthetic short fiber is less than 0.007 dtex, stable production of the fiber becomes difficult.

  The fiber length of the synthetic short fiber is preferably 1 mm or more and 10 mm or less, and more preferably 1 mm or more and 6 mm or less. If the fiber length exceeds 10 mm, formation may be poor. On the other hand, when the fiber length is less than 1 mm, the mechanical strength of the nonwoven fabric substrate may be weakened.

  In this invention, 50-100 mass% is preferable, as for the total content rate of the fibrillated heat resistant fiber and synthetic short fiber in a nonwoven fabric base material, 60-100 mass% is more preferable, and 80-100 mass% is further more preferable. If the total content is less than 50% by mass, the short-circuit defect rate may increase. The mass ratio of fibrillated heat resistant fiber: synthetic short fiber is preferably 7: 1 to 1:19, more preferably 5: 1 to 3:17, and even more preferably 4: 1 to 1: 5. When the ratio of the synthetic short fibers is more than 1:19, the heat shrinkage of the separator may be increased, and the heat resistance may be lowered. When the ratio is less than 7: 1, the puncture strength of the nonwoven fabric substrate is weakened. It may be damaged during handling or coating of the nonwoven fabric substrate.

  The nonwoven fabric substrate of the present invention may contain fibers other than fibrillated heat resistant fibers and synthetic short fibers. Examples thereof include cellulose fibers, pulped and fibrillated cellulose fibers, fibrils made of synthetic resin, pulped products, fibrillated products, and inorganic fibers. Examples of the inorganic fiber include glass, alumina, silica, ceramics, and rock wool. When inorganic fibers are contained, it is preferable because the heat resistant dimensional stability and puncture strength of the nonwoven fabric base material are improved. The cellulose fiber may be either natural cellulose or regenerated cellulose.

In the present invention, the basis weight of the nonwoven fabric base material is preferably from 8.0~20.0g / ^{m 2,} more preferably ^{9.0~19.0g / m 2, 10.0~18.0g / m} 2 is Further preferred. If it exceeds 20.0 g / m ² , the thickness of the separator may increase, and if it is less than 8.0 g / m ² , it may be difficult to obtain sufficient strength. The basis weight is measured based on the method defined in JIS P 8124 (paper and paperboard—basis weight measurement method).

  In this invention, 8-50 micrometers is preferable, as for the thickness of a nonwoven fabric base material, 9-45 micrometers is more preferable, and 10-40 micrometers is further more preferable. If it exceeds 50 μm, the resistance value of the separator may be too high, and if it is less than 8 μm, the strength of the nonwoven fabric substrate becomes too weak and may be damaged during handling or coating of the nonwoven fabric substrate. In addition, thickness means the value measured based on the method prescribed | regulated to JISB7502, ie, the value measured with the outside micrometer at the time of 5N load.

In the present invention, the density of the nonwoven fabric base material is preferably from ^{0.250~0.700g / cm 3, 0.400~0.600g / cm} 3 is more preferable. If the density is less than 0.250 g / cm ³ , short-circuiting may occur easily, and if it exceeds 0.700 g / cm ³ , the resistance value of the separator may be too high. The density is a value obtained by dividing the basis weight by the thickness (basis weight / thickness).

  In the present invention, the nonwoven fabric substrate is preferably a wet nonwoven fabric produced by a wet papermaking method. In the wet papermaking method, fibers are dispersed in water to form a uniform papermaking slurry, and this papermaking slurry is rolled up with a papermaking machine to produce a wet nonwoven fabric. Examples of the paper machine include a paper machine that independently uses a paper net such as a circular net, a long net, an inclined type, and an inclined short net, and a composite paper machine that combines a plurality of these paper nets. In the process of manufacturing a wet nonwoven fabric, a hydroentanglement process may be performed as necessary. The nonwoven fabric substrate may be subjected to processing such as heat treatment, calendar treatment, thermal calendar treatment and the like.

  The separator of the present invention comprises a non-woven fabric base material containing fibrillated heat-resistant fibers and synthetic short fibers as essential components, and a coating layer containing an inorganic filler provided on at least one surface of the non-woven fabric base material. Have Examples of inorganic fillers include calcium carbonate, sodium carbonate, alumina, gibbsite, boehmite, magnesium oxide, magnesium hydroxide, silica, titanium oxide, barium titanate, zirconium oxide, and other inorganic oxides, inorganic hydroxides, aluminum nitride, and nitride. Examples thereof include inorganic nitrides such as silicon, aluminum compounds, zeolites, and mica. Among these, alumina, boehmite, magnesium oxide, and magnesium hydroxide are preferable. The shape of the inorganic filler may be any of a spherical shape, a substantially spherical shape, a plate shape, a rectangular parallelepiped shape, a star shape, a scale shape, and an indefinite shape.

  The average particle size of the inorganic filler is preferably from 0.1 to 3.0 μm, more preferably from 0.3 to 2.5 μm, still more preferably from 0.5 to 2.0 μm. If it is less than 0.1 μm, a short circuit may occur easily. If it exceeds 3.0 μm, it may be difficult to reduce the thickness of the separator.

  The (volume) average particle diameter in the present invention is a volume average particle diameter (D50) obtained from particle size distribution measurement by a laser diffraction method.

  In the present invention, in addition to the inorganic filler, the coating layer containing the inorganic filler contains an inorganic or organic binder that is electrochemically stable and stable with respect to the electrolytic solution and can adhere the inorganic filler to the nonwoven fabric substrate. Is preferred.

  Examples of the organic binder include polyvinylidene fluoride (PVdF) and derivatives thereof, meta-type or para-type aromatic polyamide resins, polyimide resins such as aromatic polyimide, polysulfone resins, and ethylene-vinyl acetate copolymers (particularly, Copolymer of 20 to 35 mol% vinyl acetate), ethylene-acrylate copolymer, fluorine resin, styrene butadiene rubber (SBR) resin, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane Examples thereof include, but are not limited to, resins and epoxy resins. Moreover, these binders may be used individually by 1 type, and may use 2 or more types together.

  As the inorganic binder, for example, generally called a silane coupling agent, a 3-glycidyloxytrimethoxysilane or methacryloyloxypropyltrimethylsilane that chemically bonds an inorganic oxide and an organic compound through a dehydration or dealcoholization reaction or the like is used. A mixture of a silicon compound having an organic functional group such as methoxysilane or 3-aminopropyltriethoxysilane and an inorganic oxide sol such as silica or zirconium oxide is preferable because of excellent adhesion strength and heat resistance. Is not limited to this.

  In this invention, 85-99 mass% is preferable, as for content of the inorganic filler in the coating layer containing an inorganic filler, 87-99 mass% is more preferable, and 90-99 mass% is further more preferable. When it exceeds 99% by mass, the strength of the coating layer containing the inorganic filler may be weakened, and when it is less than 85% by mass, the resistance of the separator may be increased.

  In this invention, the coating layer containing an inorganic filler is obtained by the method of coating the coating liquid containing an inorganic filler on a nonwoven fabric base material.

  The medium for preparing the coating liquid containing the inorganic filler is not particularly limited as long as it can uniformly dissolve or disperse the binder and the inorganic filler. For example, aromatic hydrocarbons such as toluene, ethers such as tetrahydrofuran, etc. , Ketones such as methyl ethyl ketone, alcohols such as isopropanol, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, water and the like as necessary Can be used. Moreover, you may mix and use these media as needed.

  As a method of coating a coating liquid containing an inorganic filler on a nonwoven fabric substrate, for example, various coating methods such as blade, rod, reverse roll, lip, die, curtain, air knife, flexo, screen, offset, gravure, Various printing methods such as inkjet, transfer methods such as roll transfer and film transfer, pulling methods such as dipping, and the like can be selected and used as necessary. During coating, the nonwoven fabric substrate and process paper may be applied in layers, and the process paper may be peeled off after drying.

The coating amount of the coating layer containing an inorganic filler (bone dry) is preferably from 1.5~14.0g / ^{m 2,} more preferably 3.0~13.0g / ^{m 2,} 5.0~12.0g / M ² is more preferable. Exceeds 14.0 g / ^{m 2,} there is a case where the thickness of the separator is increased, is less than 1.5 g / ^{m 2,} there is a case where short circuit is likely to occur.

The basis weight of the separator for a solid electrolytic capacitor of the present invention is preferably 9.5~34.0g / ^{m 2,} more preferably ^{12.0~32.0g / m 2, 15.0~30.0g / m} 2 Is more preferable. If it exceeds 34.0 g / m ² , the resistance of the separator may be too high, and if it is less than 9.5 g / m ² , short-circuiting is likely to occur or it is difficult to obtain sufficient strength. There is a case.

  9-55 micrometers is preferable, as for the thickness of the separator for solid electrolytic capacitors of this invention, 11-50 micrometers is more preferable, and 13-45 micrometers is more preferable. If it exceeds 55 μm, the thickness of the separator becomes too thick, and the resistance of the separator may become too high. If it is less than 9 μm, short-circuiting is likely to occur or it is difficult to obtain sufficient strength. There is a case.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a present Example.

<Nonwoven fabric substrate 1, 4, 5, 6, 7>
Slurries 1, 4, 5, 6, and 7 shown in Table 1 were prepared, wet papermaking was performed using a circular paper machine, both surfaces were brought into contact with a metal roll heated to 200 ° C., and heat treatment was performed. Then, the thickness was adjusted, and nonwoven fabric substrates 1, 4, 5, 6, and 7 were produced.

<Nonwoven fabric base materials 2, 3>
Slurries 2 and 3 shown in Table 1 were prepared, wet papermaking was carried out using a circular paper machine, and then calendered to adjust the thickness to produce nonwoven substrates 2 and 3.

<Nonwoven fabric substrate 8>
After preparing slurry 8 shown in Table 1 and wet papermaking using a circular paper machine, both sides were brought into contact with a metal roll heated to 200 ° C. and heat treated, and further calendered to adjust the thickness. Material 8 was produced.

<Nonwoven fabric substrate 9, paper substrate 11>
Slurries 9 and 11 shown in Table 1 were prepared, and wet papermaking was performed using a circular net paper machine. Then, the thickness was adjusted by calendering to prepare a nonwoven fabric base material 9 and a paper base material 11.

<Nonwoven fabric substrate 10>
Slurry 10 shown in Table 1 was prepared, and wet papermaking was performed using a circular paper machine. However, since the fibrillated wholly aromatic polyamide fiber had no binding force, a nonwoven fabric substrate could not be produced.

  In Table 1, A1, A3, and A6 are fibrillated wholly aromatic polyamides, A2 is fibrillated wholly aromatic polyester, A4 is fibrillated polyimide, and A5 is fibrillated polyphenylene sulfide. As shown in Table 1. B1 is a polyester short fiber having a fineness of 0.06 dtex and a fiber length of 3 mm (manufactured by Teijin Fibers, trade name: TP04N), B2 is a heat-sealable core-sheath polyester short fiber having a fineness of 1.1 dtex and a fiber length of 5 mm (manufactured by Teijin Fibers, (Brand name: TJ04CN), B3 has a fineness of 0.1 dtex and a fiber length of 3 mm acrylic short fiber (manufactured by Mitsubishi Rayon, trade name: Bonnell (registered trademark)), B4 has a fineness of 0.3 dtex and a fiber length of 3 mm nylon 6,6 Short fiber, B5 means polyvinyl alcohol short fiber (made by Kuraray, trade name: VPB107-1 × 3). C1 means Canadian hemp pulp with a standard freeness of 500 ml. Table 2 shows the basis weight, thickness, and density of each nonwoven fabric substrate and paper substrate.

<Preparation of coating liquid a1>
In a dispersion obtained by dispersing 100 parts by mass of boehmite having an average particle size of 0.5 μm in 150 parts by mass of water, 75 parts by mass of a 2% by mass aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 200 mPa · s of a 1% by mass aqueous solution at 25 ° C. Was added and stirred and mixed, and 10 parts of a carboxy-modified styrene-butadiene copolymer resin emulsion (solid content concentration 50% by mass) having a glass transition point of −18 ° C. and a volume average particle size of 0.2 μm was added and stirred and mixed. Adjustment water was added to adjust the solid content concentration to 25% by mass to prepare a coating liquid a1.

<Preparation of coating liquid a2>
In a dispersion obtained by dispersing 100 parts by mass of magnesium hydroxide having an average particle diameter of 1.0 μm in 150 parts by mass of water, a 1% by mass aqueous solution of carboxymethylcellulose sodium salt having a viscosity at 25 ° C. of 200 mPa · s is 2% by mass. Add part by mass and stir and mix, add 10 parts by mass of carboxy-modified styrene-butadiene copolymer resin emulsion (solid content concentration 50% by mass) having a glass transition point of -18 ° C. and a volume average particle size of 0.2 μm, and stir and mix. Finally, adjustment water was added to adjust the solid content concentration to 25% by mass to prepare a coating liquid a2.

<Separator for solid electrolytic capacitor>
(Examples 1-4)
On the nonwoven fabric base materials 1 to 4, the coating liquid a1 is coated and dried with a kiss reverse gravure coater so that the coating amount (absolute dryness) is 10.0 g / m ² . The separator for solid electrolytic capacitors of Examples 1-4 shown in Table 3 was obtained.

(Examples 5-7)
On the nonwoven fabric substrates 5 to 7, the coating liquid a2 is coated and dried with a kiss reverse gravure coater so that the coating amount (absolutely dry) is 10.0 g / m ² . The separator for solid electrolytic capacitors of Examples 5-7 shown in Table 3 was obtained.

(Comparative Examples 1 and 2)
On the nonwoven fabric substrates 8 and 9, the coating liquid a1 is coated and dried with a kiss reverse gravure coater so that the coating amount (absolute dryness) is 10.0 g / m ² . The separator for solid electrolytic capacitors of Examples 5-7 shown in Table 3 was obtained.

(Comparative Example 3)
Since the nonwoven fabric substrate 10 could not be produced, the solid electrolytic capacitor separator of Comparative Example 3 could not be produced.

(Comparative Example 4)
The paper substrate 11 was used as the solid electrolytic capacitor separator of Comparative Example 4.

  The separators for solid electrolytic capacitors of Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 3.

<Production of Solid Electrolytic Capacitors for Evaluation of Examples 1 to 7 and Comparative Examples 1 and 2>
An aluminum foil with a dielectric film formed after etching the surface was roughened for the anode, and an aluminum foil without a dielectric film was used for the cathode. A solid electrolytic capacitor separator is placed between the anode and the cathode using the solid electrolytic capacitor separator of Examples 1 to 7 and Comparative Examples 1 and 2 slitted in advance to a predetermined width and wound. A winding element of a solid electrolytic capacitor was produced. At this time, the coating layer surface of the separator was the cathode side. The winding element of the solid electrolytic capacitor was immersed in a solution mixed at a mass ratio of 3,4-ethylenedioxythiophene: iron (III) p-toluenesulfonate: n-butyl alcohol = 34: 33: 33 at 200 ° C. The polythiophene was polymerized by heat treatment for 5 minutes to obtain a solid electrolytic capacitor element. Next, the solid electrolytic capacitor element was housed in a cylindrical case to produce a solid electrolytic capacitor.

<Production of Solid Electrolytic Capacitor for Evaluation of Comparative Example 4>
An aluminum foil with a dielectric film formed after etching the surface was roughened for the anode, and an aluminum foil without a dielectric film was used for the cathode. Using a solid electrolytic capacitor separator of Comparative Example 4 that was slit in advance to a predetermined width, a solid electrolytic capacitor separator was placed between the anode and the cathode, and wound up. Was made. At this time, the coating layer surface of the separator was the cathode side. After heating the winding element of the solid electrolytic capacitor at 230 ° C. for 2 hours to carbonize the separator, the element was subjected to 3,4-ethylenedioxythiophene: iron (III) p-toluenesulfonate: n-butyl alcohol = It was immersed in a solution mixed at a mass ratio of 34:33:33 and heat-treated at 200 ° C. for 5 minutes to polymerize polythiophene to obtain a solid electrolytic capacitor element. Next, the solid electrolytic capacitor element was housed in a cylindrical case to produce a solid electrolytic capacitor.

[Short defect rate]
The presence or absence of conduction of the solid electrolytic capacitors produced using the separators of Examples and Comparative Examples was confirmed with a tester. Ten solid electrolytic capacitors were tested. If the number of conductive capacitors was 0, “◯”, 1 if “Δ”, 2 or more, “x”, and shown in Table 3.

[Heat-resistant]
The separator was cut into 200 mm width × 200 mm length, and allowed to stand in a constant temperature dryer at 200 ° C. for 3 hours, and the shrinkage in the length direction and width direction was calculated. “◯” if the average shrinkage in the length direction and width direction is less than 0.8%, “△” if it is 0.8% or more and less than 1.0%, and if it is 1.0% or more. It is represented by “x” and shown in Table 3.

  The separator for solid electrolytic capacitors of Examples 1 to 7 is an inorganic material formed on at least one surface of the non-woven fabric substrate containing fibrillated heat-resistant fibers and synthetic short fibers as essential components, and the non-woven fabric substrate. Since it has a coating layer containing a filler, the short-circuit defect rate was low and the heat resistance was excellent.

  On the other hand, the solid electrolytic capacitor separators of Comparative Examples 1 and 2 were inferior in heat resistance because they did not contain fibrillated heat resistant fibers.

  Although the comparative example 3 tried preparation of the nonwoven fabric base material 10 only with a fibrillated heat-resistant fiber, since this fiber had no binding force, the nonwoven fabric base material 10 was not able to be manufactured.

  The separator for the solid electrolytic capacitor of Comparative Example 4 did not contain fibrillated heat-resistant fibers and synthetic short fibers, and was a paper base material composed only of natural pulp, so the short defect rate was poor and the heat resistance was poor.

  The solid electrolytic capacitor separator of Example 1 was slightly inferior in heat resistance compared to the solid electrolytic capacitor separators of Examples 2 to 7 because the content of fibrillated heat resistant fibers was slightly less.

  The separator for the solid electrolytic capacitor of Example 7 had a slightly large Canadian standard freeness of fibrillated heat resistant fiber, so the nonwoven fabric substrate was slightly rough, and the uniformity of the coating layer containing the inorganic filler was slightly worse. Therefore, the short-circuit defect rate was slightly inferior to the solid electrolytic capacitor separators of Examples 1 to 6.

  As an application example of the present invention, a solid electrolytic capacitor separator is suitable. Moreover, it can utilize also for the hybrid capacitor represented by the lithium ion capacitor.

Claims (2)

  A solid comprising: a nonwoven fabric base material containing fibrillated heat-resistant fibers and synthetic short fibers as essential components; and a coating layer containing an inorganic filler provided on at least one surface of the nonwoven fabric. Electrolytic capacitor separator.   The separator for a solid electrolytic capacitor according to claim 1, wherein the fibrillated heat resistant fiber is a fibrillated wholly aromatic polyamide fiber.